"From now until 10pm on June 23 we will not rest and I will not stop explaining why nine million Labour voters have most to gain from remaining in the EU," he will say.

"Today I am setting out a positive agenda for Labour voters - reasons why Labour voters should vote Remain and the patriotic case for remaining in Europe.

"But we shouldn't just be a member of the European Union. We must be the leader of the European Union."

Mr Brown will argue that reforms to digital, energy and service sectors could create an estimated 500,000 new jobs in Britain over 10 years - and that a pooled energy strategy could cut domestic bills.

Mr Benn will use a speech to say the Leave camp "sound as if they mourn for the bygone age in which Britain gained influence through military strength and Empire...

"In the second half of the 20th century, we came to realise that it was far better and far more effective to be a global power that achieved its goals through co-operation rather than conquest."

Labour leader Jeremy Corbyn has been accused of dragging his heels on the referendum (Image: John Linton/PA Wire)

"We have now reached the defining moment in this referendum. The Brexit train is threatening to pull away from the station with Nigel Farage, Boris Johnson and Michael Gove in charge, taking us down a track that can only lead to disaster.

"It would make us poorer, less powerful and it would hurt the next generation as they try to prosper in tomorrow's world. That's why it is so important that we make the patriotic case for remaining in the EU and keeping Britain great."

Shadow chancellor John McDonnell MP said: "Labour wants to better use the EU's levers of power to help British families get more control against the growing economic forces of globalisation."

Some 20 of the party's MPs have signed a letter calling for Labour voices to be given more media airtime amid complaints coverage has centred on Conservative-led "fear" messages.